Sensors for water analysis are used, e.g., in chemical industry, pharmaceutical industry, semiconductor production, cooling water monitoring, drinking water and ground water analysis and monitoring, and in power plants, in which water used for for driving steam turbines is monitored for traces of contaminants.
Such sensors may, e.g., be pH sensors, conductivity sensors, oxygen sensors or ion sensitive sensors, depending on the property of the water to be sensed and on the specific application.
Detachable connections connecting a sensor to a body containing the water to be monitored in a watertight, preferably even pressure-tight manner are known in the art.
One such connection, e.g., the so-called NPT joint known in the USA, comprises a threaded joint having a conical thread, wherein PTFE (polytetrafluoroethylene) tape is attached to the joint for sealing the connection. The manufacture of such conical threads is costly, because low tolerances have to be met and stainless steel is usually used. In addition, quite some experience and skills and force is required for screwing in and unscrewing the sensor without provoking damage. If too little PTFE tape and/or a too high torque is applied, griping may occur.
Another such connection, which is easier to handle, makes use of a bayonet joint. Such connections are sometimes referred to as “quick lock”. An elastomer ring is used for sealing, and a clockwise rotation of the sensor with respect to the body results in a fixed and tight connection, and counter-clockwise rotation allows to separate the sensor from the body. Also this kind of connection is costly to manufacture and often requires quite some force for establishing the connection. Another disadvantage is, that the rotational movement of the sensor with respect to the elastomer ring causes a considerable amount of friction and can result in damage of the elastomer ring and/or of the sensor, in particular if a particle happens to be located between the elastomer ring and the sensor.